confile: handle overflow in lxc.time.offset.{boot,monotonic}

src/lxc/confile.c

@@ -2831,22 +2831,26 @@ static int set_config_time_offset_boot(const char *key, const char *value,
 	if (ret)
 		return ret;
 
-	/* TODO: Handle overflow. */
 	unit = lxc_trim_whitespace_in_place(buf);
-	if (strcmp(unit, "h") == 0)
-		lxc_conf->timens.s_boot = offset * 3600;
-	else if (strcmp(unit, "m") == 0)
-		lxc_conf->timens.s_boot = offset * 60;
-	else if (strcmp(unit, "s") == 0)
+	if (strcmp(unit, "h") == 0) {
+		if (!multiply_overflow(offset, 3600, &lxc_conf->timens.s_boot))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "m") == 0) {
+		if (!multiply_overflow(offset, 60, &lxc_conf->timens.s_boot))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "s") == 0) {
 		lxc_conf->timens.s_boot = offset;
-	else if (strcmp(unit, "ms") == 0)
-		lxc_conf->timens.ns_boot = offset * 1000000;
-	else if (strcmp(unit, "us") == 0)
-		lxc_conf->timens.ns_boot = offset * 1000;
-	else if (strcmp(unit, "ns") == 0)
+	} else if (strcmp(unit, "ms") == 0) {
+		if (!multiply_overflow(offset, 1000000, &lxc_conf->timens.ns_boot))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "us") == 0) {
+		if (!multiply_overflow(offset, 1000, &lxc_conf->timens.ns_boot))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "ns") == 0) {
 		lxc_conf->timens.ns_boot = offset;
-	else
+	} else {
 		return ret_errno(EINVAL);
+	}
 
 	return 0;
 }
@@ -2866,22 +2870,26 @@ static int set_config_time_offset_monotonic(const char *key, const char *value,
 	if (ret)
 		return ret;
 
-	// TODO: Handle overflow.
 	unit = lxc_trim_whitespace_in_place(buf);
-	if (strcmp(unit, "h") == 0)
-		lxc_conf->timens.s_monotonic = offset * 3600;
-	else if (strcmp(unit, "m") == 0)
-		lxc_conf->timens.s_monotonic = offset * 60;
-	else if (strcmp(unit, "s") == 0)
+	if (strcmp(unit, "h") == 0) {
+		if (!multiply_overflow(offset, 3600, &lxc_conf->timens.s_monotonic))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "m") == 0) {
+		if (!multiply_overflow(offset, 60, &lxc_conf->timens.s_monotonic))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "s") == 0) {
 		lxc_conf->timens.s_monotonic = offset;
-	else if (strcmp(unit, "ms") == 0)
-		lxc_conf->timens.ns_monotonic = offset * 1000000;
-	else if (strcmp(unit, "us") == 0)
-		lxc_conf->timens.ns_monotonic = offset * 1000;
-	else if (strcmp(unit, "ns") == 0)
+	} else if (strcmp(unit, "ms") == 0) {
+		if (!multiply_overflow(offset, 1000000, &lxc_conf->timens.ns_monotonic))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "us") == 0) {
+		if (!multiply_overflow(offset, 1000, &lxc_conf->timens.ns_monotonic))
+			return -EOVERFLOW;
+	} else if (strcmp(unit, "ns") == 0) {
 		lxc_conf->timens.ns_monotonic = offset;
-	else
+	} else {
 		return ret_errno(EINVAL);
+	}
 
 	return 0;
 }

src/lxc/utils.c

@@ -1904,3 +1904,15 @@ int fix_stdio_permissions(uid_t uid)
 
 	return fret;
 }
+
+bool multiply_overflow(int64_t base, uint64_t mult, int64_t *res)
+{
+	if (base > 0 && base > (INT64_MAX / mult))
+		return false;
+
+	if (base < 0 && base < (INT64_MIN / mult))
+		return false;
+
+	*res = base * mult;
+	return true;
+}

src/lxc/utils.h

@@ -251,4 +251,6 @@ static inline bool gid_valid(gid_t gid)
 	return gid != LXC_INVALID_GID;
 }
 
+extern bool multiply_overflow(int64_t base, uint64_t mult, int64_t *res);
+
 #endif /* __LXC_UTILS_H */